Synthesis of organic liquid crystals containing selectively fluorinated cyclopropanes

• Zeguo Fang,
• Nawaf Al-Maharik,
• Peer Kirsch,
• Matthias Bremer,
• Alexandra M. Z. Slawin and
• David O’Hagan

Beilstein J. Org. Chem. 2020, 16, 674–680, doi:10.3762/bjoc.16.65

• exhibited smectic phases with low levels of negative dielectric anisotropy. The relatively high positive dielectric anisotropy of compound 11a indicates that the configurational constrained motif is required to increase the magnitude of the Δε parameter. Although it proved challenging to isolate a

• –11a With the four difluorocyclopropanes 8–11a in hand, our attention focused on an experimental evaluation of their thermodynamic and physical properties, such as birefringence (Δn) and dielectric anisotropy (Δε). DSC and POM analysis (Table 1) indicated that only compounds 8 and 9 exhibited smectic

• phases. The smectic phase of LC 8 was maintained over a broad temperature range (54–84 °C), whereas that for 10 and 11a only showed a melting point and these compounds did not display any obvious liquid crystallinity (Table 1). Therefore, any development of these latter materials would require extended

Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

• Afef Mabrouki,
• Malek Fouzai,
• Armand Soldera,
• Abdelkader Kriaa and
• Ahmed Hedhli

Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17

• , which generates a lamellar packing and thus contributes to smectic phase stability [14]. It was reported that even simple n-alkanes containing a fluorocarbon block produces smectic phases [15][16][17][18][19]. Some molecules having only a single aromatic ring and fluorinated tail show smectic phases

• realized in cooling and heating cycles for compounds 2b, 4a and 4b (Figure 2). POM technique has illustrated smectic phases for all compounds. Identification of the phase textures was accomplished by comparing with those reported in literature [24]. The texture of 2b (Figure 2a) seems to be a variant of

Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

• Alexej Bubnov,
• Miroslav Kašpar,
• Věra Hamplová,
• Ute Dawin and
• Frank Giesselmann

Beilstein J. Org. Chem. 2013, 9, 425–436, doi:10.3762/bjoc.9.45

• . Four of these nonchiral and chiral materials exhibit nematic and chiral nematic phases, respectively. For some molecular structures, smectic phases have also been detected. A contact sample of one of the prepared compounds with diethylene glycol clearly shows the lyotropic behaviour; namely a lamellar

• systems composed of amphiphilic molecules can exhibit smectic phases with layered structure [2] or nematic (eventually cholesteric) phases. Lyotropic systems usually form a lamellar liquid-crystalline mesophase, i.e., a lyotropic analogue of the thermotropic orthogonal smectic A (SmA) phase [3], and more

• also the chiral smectic phases. No pronounced difference in clearing point has been found in cases where the molecule core is the same as for TL5 but the nonchiral chain with a double bond is replaced by that with two hydroxy groups. However, a minor increase in the melting point (about 10 K) has been

Formation of smectic phases in binary liquid crystal mixtures with a huge length ratio

• Nadia Kapernaum,
• Friederike Knecht,
• C. Scott Hartley,
• Jeffrey C. Roberts,
• Robert P. Lemieux and
• Frank Giesselmann

Beilstein J. Org. Chem. 2012, 8, 1118–1125, doi:10.3762/bjoc.8.124

• phase of the longer mesogen was identified as a smectic F phase. Keywords: bidispersity; liquid crystals; phase diagrams; smectic phases; smectic F phase; structure and dynamics; Introduction The mixing of different liquid crystals is a common technique to tailor their properties for specific

• experimental data and reflects the molecular ordering in the smectic phases of bidisperse molecules best. The preference for the SmA over the SmC phase, which was observed for all systems with a large length ratio, may also be explained by extensive out-of-layer fluctuations [2]. The molecules in a nontilted

• texture observations suggest that the higher-ordered smectic phase must be a tilted phase. A demonstration that the sample is shearable ruled out soft-crystalline phases (E, G, H, J and K), leaving only the two fluid, higher-ordered, hexatic smectic phases SmF and SmI as possibilities. To distinguish

Liquid-crystalline heterodimesogens and ABA-heterotrimesogens comprising a bent 3,5-diphenyl-1,2,4-oxadiazole central unit

• Govindaswamy Shanker,
• Marko Prehm and
• Carsten Tschierske

Beilstein J. Org. Chem. 2012, 8, 472–485, doi:10.3762/bjoc.8.54

• studied. These compounds are of interest with respect to the potential biaxiality of the nematic (N) [45][50][57] and nontilted smectic phases of these compounds [45]. Bent-core units have also been combined with disc-like units, but in this case the incompatibility and steric mismatch of the distinct

• between the Ncyb phases and undistorted smectic phases have been observed previously and seem to represent a typical phenomenon for molecules at the borderline between a bent-core and rod-like shape. Dimesogens Thia-Ox/n The dimesogens Thia-Ox/5 and Thia-Ox/10 have a molecular structure that is quite

• with the C5 spacers are organized side-by-side and separated from the alkyl chains in the monolayer smectic phases and in the cybotactic clusters of the nematic phase (Figure 4a), in the case of compound Thia-Ox/10 the longer C10 spacers cannot be accommodated between the aromatic cores. These long

Perhydroazulene-based liquid-crystalline materials with smectic phases

• Zakir Hussain,
• Henning Hopf and
• S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 403–410, doi:10.3762/bjoc.8.44

• . The mesomorphic properties of the new LC compounds were investigated by differential scanning colorimetry, polarizing optical microscopy and X-ray diffraction. We report here on the LC properties of nonchiral materials, which predominantly exhibit smectic phases and display nematic phases only within

• ; nematic phases; smectic phases; Introduction Liquid crystals for display applications have to fulfill a complex, interdependent set of properties [1]. First of all, they must display a broad nematic phase, typically ranging from −30 °C to +80 °C. The absolute value for the dielectric anisotropy Δε should

• that are observed in isomers with only trans-positioned terminal groups. We have also shown that by changing terminal group(s), a broad range of LC phases results, characterized by the transition temperatures of smectic phases in those isomers that carry a polar terminal group compared to those with a

Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls

• Katharina C. Kress,
• Martin Kaller,
• Kirill V. Axenov,
• Stefan Tussetschläger and
• Sabine Laschat

Beilstein J. Org. Chem. 2012, 8, 371–378, doi:10.3762/bjoc.8.40

• malonates and cyanoacetates are well known as suitable ligands for strong coordination of main-group and transition metals [25]. Benzylidene derivatives of malonic esters, so called swallow-tailed liquid crystals, were described as forming smectic phases [26]. However, most work on liquid-crystalline

Liquid-crystalline nanoparticles: Hybrid design and mesophase structures

• Gareth L. Nealon,
• Romain Greget,
• Cristina Dominguez,
• Zsuzsanna T. Nagy,
• Daniel Guillon,
• Jean-Louis Gallani and
• Bertrand Donnio

Beilstein J. Org. Chem. 2012, 8, 349–370, doi:10.3762/bjoc.8.39

• , based on the shape and chemical characteristics of the mesogen under investigation. The simplest is the nematic phase, whereby the mesogenic moieties exhibit an average alignment along a common direction (or director), whereas the smectic phases also display a degree of positional ordering (i.e., the

• in the primary grafting layer. In these cases, particles that were grafted with short hexanethiols in the primary layer (Au@C6/71,6 and Au@C6/72,5) exhibited smectic phases, whilst increasing the length of the n-alkylthiols invoked the formation of modulated smectic and columnar phases (Figure 10

• ). Whilst the particles coated with proto-mesogenic hemi-phasmidic ligands 812,12,12 and 80,12,12 (Figure 8) displayed only short-range positional order, particles coated with the single-chain mesogenic ligand 80,8,0 (Figure 8) displayed smectic phases, irrespective of the length of the primary grafting

Laterally substituted symmetric and nonsymmetric salicylideneimine-based bent-core mesogens

• Sonja Findeisen-Tandel,
• Wolfgang Weissflog,
• Ute Baumeister,
• Gerhard Pelzl,
• H. N. Shreenivasa Murthy and
• Channabasaveshwar V. Yelamaggad

Beilstein J. Org. Chem. 2012, 8, 129–154, doi:10.3762/bjoc.8.15

• corresponding molecular movements, is sensitive to variations in the molecular structure. Keywords: antiferroelectric smectic phases; bent-core mesogens; electro-optical behaviour; liquid crystals; salicylideneanilines; Introduction For a long time there was a general perception that molecules capable of

• exhibiting liquid crystal (LC) phases have to be rodlike, so-called calamitic LCs. As is well known, such compounds exhibit nematic and smectic phases, which are commonly referred to as “calamitic phases”. However, the inherent fallacy of this notion was pointed out in the middle of the seventies when

• compounds have been synthesized with various combinations of structural fragments, and thus, they represent a new subfield of liquid crystals. Generally speaking, these mesogens prefer to pack in layers so as to yield smectic phases. Due to their bent shape there is a lateral correlation of molecular

Ring-alkyl connecting group effect on mesogenic properties of p-carborane derivatives and their hydrocarbon analogues

• Aleksandra Jankowiak,
• Piotr Kaszynski,
• William R. Tilford,
• Kiminori Ohta,
• Adam Januszko,
• Takashi Nagamine and
• Yasuyuki Endo

Beilstein J. Org. Chem. 2009, 5, No. 83, doi:10.3762/bjoc.5.83

• (SmA and SmB), while the terphenyl analogues display a rich smectic polymorphism involving mainly tilted phases. The terphenyl derivatives 14D[6] and 16D[6] exhibit the most interesting polymorphism in the series with 4 smectic phases and possibly a soft crystalline modification such as a G phase below

Molecular length distribution and the formation of smectic phases

• Nadia Kapernaum,
• C. Scott Hartley,
• Jeffrey C. Roberts,
• Robert P. Lemieux and
• Frank Giesselmann

Beilstein J. Org. Chem. 2009, 5, No. 65, doi:10.3762/bjoc.5.65

• transition. Thus smectic A seems to be the most stable phase to accommodate mesogenic molecules of substantially different length. These surprising results are of general interest for the understanding of the structure and dynamics of smectic phases, as the structure of these bidisperse smectics is signified

• by extensive out-of-layer fluctuations. Keywords: bidispersity; liquid crystals; phase diagrams; smectic phases; structure and dynamics; Introduction The classical (and highly successful) approach to systematically tailor liquid crystal materials for specific applications is the formulation of

• order – to be the ideal liquid crystalline (LC) phase for accommodating molecules of substantially different lengths. On the other hand the smectic phases – due to their layer structure – seem to be unsuited to accommodate molecules of different lengths. Comparing SmC and SmA, the SmC phase might be

A convenient method for preparing rigid-core ionic liquid crystals

• Julien Fouchet,
• Laurent Douce,
• Benoît Heinrich,
• Richard Welter and
• Alain Louati

Beilstein J. Org. Chem. 2009, 5, No. 51, doi:10.3762/bjoc.5.51

• along an orientational axis), smectic phases (orientational/positional order in the layers) and columnar phases (orientational/positional order in the columns). The lyotropic compounds display not only lamellar and columnar organization but also hierarchical self-assembly in spheres (micelles), ribbons

Progress in liquid crystal chemistry

• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 48, doi:10.3762/bjoc.5.48

• smectic phases, nematic phase engineering by using V-shaped molecules, saddle-shaped columnar systems displaying anomalous odd-even effects, theoretical studies on the origin of chirality transfer in liquid crystalline host-guest systems, liquid crystalline carboranes and dyes and discotic phenanthrene